The present invention relates to a drink-stirring device for stirring or mixing liquid and/or powdered ingredients with liquid in a drinking vessel. The invention also relates to a method for stirring, and eventually foaming, a liquid in a drinking vessel. Stirring devices of this kind are used in apparatus for the retail sale of drinks consisting of a usually hot liquid and liquid or powdered concentrate.
It has often been difficult for previously known stirring devices to bring about satisfactory mixing of the other ingredients with the liquid. Particular problems arise when it is desirable to bring about frothing of liquid, for example when preparing cappuccino. This is usually carried out now by frothing milk in a separate vessel. This vessel has to be washed several times a day for reasons of hygiene. EP 1 197 145 describes a device for frothing milk for preparing cappuccino consisting of a tubular device with a through-spindle with stirring blade, an inlet for steam at the top and inlet openings for air and milk along the tube. This is an expensive and complicated stirring device of great overall height, and furthermore it cannot prepare the whole drink but only the milk froth. It is generally the case that two stirring devices are required for making cappuccino.
It is known to use permanent magnets in mixing vessels, these magnets being caused to rotate by means of an outer rotating or pole-changing magnetic field. WO 85/05046 discloses such a device comprising a mixing vessel with a bottom outlet. Arranged round the lower edge of the vessel is a closed iron core with a number of electric coils connected to an alternating current source, which can produce magnetic fields of varying frequency and strength. The device is used especially for mixing in connection with chemical processes.
EP 0 285 210 describes a drink mixer comprising a tube-like mixing vessel with a bottom outlet. Arranged in the mixing vessel is a mixer blade, which has at the bottom a magnetic member in the form of a permanent magnet. Arranged outside the vessel is an electromagnet, which can set the mixer blade in rotating and/or vibrating motion. The mixer blade is exposed in the mixing vessel and can easily be lifted out for cleaning. Cleaning nevertheless remains a laborious and time-consuming operation. The mixer blade can be provided with slits in order to bring about frothing of the drink, for example when preparing cappuccino. Cleaning is then even more laborious.
EP 1 155 646 discloses a device for preparing a drink in a cup, into which powdered ingredients have first been introduced. Liquid for diluting the drink is supplied through a distributing head arranged on a vertical hollow shank attached to a drive wheel. At the top, the shank is connected to an inlet tube via a freely rotatable coupling. The distributing head comprises a diagonally extending connecting line, which leads to two opposite, eccentrically positioned, downwardly directed distributing nozzles. The drive wheel is arranged in a gearbox and is driven by an electric motor.
This device has a number of disadvantages. It comprises an extra motor and a mechanical transmission to the distributing head via gearwheels. This leads to wear and a risk of breakdown. The freely rotating connection between the tube and the hollow shank is also subjected to wear and, over time, suffers liquid leakage. The winding liquid passages in the distributing head are also difficult of access for cleaning, and scale can be expected to be deposited in these.